diff --git a/m4/fp_setup_project_version.m4 b/m4/fp_setup_project_version.m4
index 26df01865b1b0f118f7a9375ac8d1d47c072fdf5..d51759add71aa22f2c06264109262693efaf05a2 100644
--- a/m4/fp_setup_project_version.m4
+++ b/m4/fp_setup_project_version.m4
@@ -77,6 +77,10 @@ AC_DEFUN([FP_SETUP_PROJECT_VERSION],
     ProjectPatchLevel1=`echo $ProjectPatchLevel | sed 's/^\(@<:@^.@:>@*\)\(\.\{0,1\}\(.*\)\)$/\1/'`
     ProjectPatchLevel2=`echo $ProjectPatchLevel | sed 's/^\(@<:@^.@:>@*\)\(\.\{0,1\}\(.*\)\)$/\3/'`
 
+    # The project patchlevel1/2 is zero unless stated otherwise
+    test -z "$ProjectPatchLevel1" && ProjectPatchLevel1=0
+    test -z "$ProjectPatchLevel2" && ProjectPatchLevel2=0
+
     AC_SUBST([ProjectPatchLevel1])
     AC_SUBST([ProjectPatchLevel2])
 
diff --git a/testsuite/tests/driver/all.T b/testsuite/tests/driver/all.T
index 907002fcf7094e8f8ffe81d638ffed5aa80a8a7b..af81d61eb86bf51a503b313a69b546ef7f87d426 100644
--- a/testsuite/tests/driver/all.T
+++ b/testsuite/tests/driver/all.T
@@ -303,3 +303,4 @@ test('T20200loop', extra_files(['T20200loop']), multimod_compile,
      ['Datatypes', '-iT20200loop -O -v0'])
 test('T20316', normal, makefile_test, [])
 test('MultiRootsErr', normal, multimod_compile_fail, ['MultiRootsErr', 'MultiRootsErr'])
+test('patch-level2', normal, compile, ['-Wcpp-undef'])
diff --git a/testsuite/tests/driver/patch-level2.hs b/testsuite/tests/driver/patch-level2.hs
new file mode 100644
index 0000000000000000000000000000000000000000..ae89fbed8ed8320774f3c14611d5ae00b7d5d795
--- /dev/null
+++ b/testsuite/tests/driver/patch-level2.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE CPP #-}
+module PatchLevel2 where
+
+
+p2 = __GLASGOW_HASKELL_PATCHLEVEL2__
+p1 = __GLASGOW_HASKELL_PATCHLEVEL1__